Bond length in a diatomic molecule is best approximated by which relation?

Bond length in a diatomic molecule is best approximated by which relation?

• A. Difference of radii
• B. Product of radii
• C. Sum of radii
• D. Half of sum

Answer: (D)

Bond length is the distance between the two nuclei in a diatomic molecule. In covalent bonding, each atom has a covalent radius that describes how far its electron density extends toward its partner. When the two atoms form a bond, their electron clouds meet, and the nuclei sit apart by roughly the sum of these two radii. So the bond length is well estimated by adding the covalent radii of the two atoms. This simple relation captures why smaller atoms with smaller radii have shorter bonds and larger atoms with bigger radii have longer bonds, and it aligns with typical measurements across many diatomics (for example, H–H is about 0.74 Å, matching 0.37 Å + 0.37 Å). The idea of taking half of the sum would not correspond to the actual nucleus-to-nucleus distance, which is why the sum is the standard estimate.

Bond length is the distance between the two nuclei in a diatomic molecule. In covalent bonding, each atom has a covalent radius that describes how far its electron density extends toward its partner. When the two atoms form a bond, their electron clouds meet, and the nuclei sit apart by roughly the sum of these two radii. So the bond length is well estimated by adding the covalent radii of the two atoms. This simple relation captures why smaller atoms with smaller radii have shorter bonds and larger atoms with bigger radii have longer bonds, and it aligns with typical measurements across many diatomics (for example, H–H is about 0.74 Å, matching 0.37 Å + 0.37 Å). The idea of taking half of the sum would not correspond to the actual nucleus-to-nucleus distance, which is why the sum is the standard estimate.